Multiple Screen Detection Systems

ABSTRACT

The present specification discloses an improved detection system employing multiple screens for greater detection efficiency. More particularly, a first enclosure has two adjacent walls, each with interior surfaces, a first end and a second end. The first ends of the two adjacent walls are connected at an angle to form an interior and the second ends of the two adjacent walls are connected to a semi-circular housing. At least one substrate, positioned on each of the interior surfaces of the adjacent walls, has an active area for receiving and converting electromagnetic radiation into light. A photodetector, positioned in the interior portion of the semi-circular housing, has an active area responsive to the light.

CROSS-REFERENCE OF THE INVENTION

The present specification relies on U.S. Provisional Application No.61/313,773, which was filed on Mar. 14, 2010. The present specificationis also a continuation-in-part of U.S. patent application Ser. No.12/262,631, which was filed on Oct. 31, 2008, and relies on U.S.Provisional Application No. 60/984,640, which was filed on Nov. 1, 2007for priority. All of the aforementioned applications are hereinincorporated by reference.

FIELD OF THE INVENTION

The present specification generally discloses radiant energy imagingsystems. In particular, the present specification discloses detectionsystems and methods of using the detection systems in radiant energyimaging systems. And more particularly, the present specificationdiscloses an improved detection system employing multiple screens forgreater detection efficiency.

BACKGROUND OF THE INVENTION

Security systems are presently limited in their ability to detectcontraband, weapons, explosives, and other dangerous objects concealedunder clothing. Metal detectors and chemical sniffers are commonly usedfor the detection of large metal objects and some varieties ofexplosives, however, a wide range of dangerous objects exist that cannotbe detected with these devices. Plastic and ceramic weapons developed bymodern technology increase the types of non-metallic objects thatsecurity personnel are required to detect; the alternative of manualsearching of subjects is slow, inconvenient, and is not well-toleratedby the general public, especially as a standard procedure in, forexample, airports.

Further, radiation exposure is an important consideration in X-rayconcealed object detection systems. Currently, the United Statesstandard permits a radiation exposure of 0.25 microrem per inspectionevent. It should be noted that the inspection equipment is regulated interms of the allowable limits of radiation exposure to a person perinspection event. Persons employed in high security or securedfacilities, or those who frequently travel by airlines, may be subjectedto many security examinations per year. The standard criterion thusassures that an individual inspected less than about 100 times per yearwill not receive a non-negligible radiation dose.

Conventional systems and methods for detecting objects concealed onpersons have limitations in their design and method which prohibit themfrom achieving both low dose and high image quality which areprerequisites of commercial acceptance. Specifically, conventional priorart systems for people screening are designed such that they detectradiant energy that has been transmitted through the body, scatteredfrom the body, and/or emitted from the body. In addition, inconventional people screening systems, images are produced by bodycharacteristics and any object concealed under the subject's clothing.The system operator then inspects each image for evidence of concealedobjects.

An example of such a system is described in U.S. Pat. No. RE 28544,assigned to American Science and Engineering, describes a “radiantenergy imaging apparatus comprising: a source of a pencil beam of X-rayradiant energy; radiant energy detecting means defining a curve in fixedrelationship to said source; means for scanning with said pencil beamsaid radiant energy detecting means along said curve to provide an imagesignal representative of the radiant energy response of the medium in aregion traversed by said pencil beam along a path to said detectingmeans; means for relatively displacing said region and an assemblycomprising said source and said detecting means to establish relativetranslating motion in a direction transverse to a line joining saidsource and said detecting means to produce a sequence of image signalsrepresentative of the radiant energy response of said region in twodimensions; and means responsive to said image signals for producing animage representative of said response.”

U.S. Pat. No. 5,181,234, assigned to the assignee of the presentinvention, and herein incorporated by reference, discloses “X-rayimaging apparatus for detecting a low atomic number object carried by oron a human body positioned at a distance from said apparatus comprising:x-ray source for producing a pencil beam of X-rays directed toward saidhuman body; scanning means for moving the region of intersection of saidpencil beam and said human body over the surface of said human body in ascanning cycle, said scanning cycle being sufficiently short to exposesaid human body to a low radiation dose; a detector assembly providing asignal representative of the intensity of the X-rays scattered from saidhuman body as a result of being scanned by said scanning means, saiddetector assembly being disposed on a same side of said human body assaid X-ray source and having an active area with dimensions sufficientto receive a substantial portion of said scattered X-rays to provide acoefficient of variation of less than 10 percent in said signal; anddisplay means to presenting characteristics of the detector signal to anoperator; wherein said scattered X-rays are distributed across saiddetector to create an edge effect which enhances edges of said lowatomic number object to enable detection.”

In addition, prior art baggage inspection systems include detectionmeans for both transmitted and backscattered X-rays to independentlyproduce signals from the same incident beam. The separate signals maythen be used to enhance each other to increase the system's accuracy inrecognizing low Z materials. With the incident beam being of sufficientenergy to provide both transmitted and backscattered signals, the X-rayenergy must be relatively high, making such systems undesirable forpersonnel inspection. An example of such a system is U.S. Pat. No.4,799,247, assigned to Annis et al., which discloses “a projectionimaging system for inspecting objects for highlighting low Z materialscomprising: a source of penetrating radiation, means for formingradiation emitted by said source into a beam of predeterminedcross-section and for repeatedly sweeping said beam across a line inspace, means for moving said object to be imaged relative to said sourcein a direction perpendicular to said line in space, first radiant energydetector means located to be responsive to radiant energy penetratingsaid object and emerging from said object, substantially unchanged indirection, for producing first electrical signals, second radiant energydetector means located further from said source than said object andresponsive to radiant energy scattered by said object for producingsecond electrical signals, third radiant energy detector means locatedcloser to said source than said object and responsive to radiant energyscattered by said object for producing third electrical signals, displaymeans responsive to at least a pair of said electrical signals forseparately, independently and simultaneously displaying said pair ofelectrical signals as a function of time”.

As mentioned above, conventional systems and methods have limitationsthat prohibit them from achieving both low dose and high image qualitywhich are prerequisites of commercial acceptance. In addition, inconventional people screening systems, images are produced by bodycharacteristics and any object concealed under the subject's clothing.

The prior art systems are disadvantageous, however, because they do notadequately detect plastics, ceramics, explosives, illicit drugs, andother non-metallic objects. One reason in particular is that thesematerials share the property of a relatively low atomic number (low Z).Low Z materials present a special problem in personnel inspectionbecause of the difficulty in distinguishing the low Z object from thebackground of the subject's body which also has low Z. An inspectionsystem which operates at a low level of radiation exposure is limited inits precision by the small number of X-rays that can be directed againsta person being searched. X-ray absorption and scattering further reducesthe number of X-rays available to form an image of the person and anyconcealed objects. In prior art systems, this low number of detectedX-rays has resulted in unacceptably poor image quality.

Therefore, what is needed is a method and apparatus that increases theefficiency of a detector to detect electromagnetic radiation and improvethe quality of the resultant image generated, thus reducing the overallamount of radiation required.

What is also needed is a method for using an improved radiant energyimaging system with enhanced detection capabilities.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus andmethod for increasing the efficiency of a detector to detectelectromagnetic radiation and improve the quality of the resultant imagegenerated, thus reducing the overall amount of radiation required.

It is another object of the present invention to provide a detectorconfiguration that maximizes the efficiency of the detector material. Itis yet another object of the present invention to absorb more X-rayphotons and thus, improve detection capability.

In one embodiment, the present invention is a detection system fordetecting electromagnetic radiation comprising: an enclosure having fouradjacent walls, connected to each other at an angle and forming arectangle and interior portion of the enclosure; a front side area and aback side area formed from the four adjacent walls and located at eachend of the enclosure; a plurality of screens, wherein each screenfurther comprises an active area for receiving and convertingelectromagnetic radiation into light; and a photodetector, positioned inthe interior portion of the enclosure, having an active area responsiveto the light.

In another embodiment, the present invention is a detection system fordetecting electromagnetic radiation comprising: an enclosure having fouradjacent walls, connected to each other at an angle and forming arectangle and interior portion of the enclosure; a front side area and aback side area formed from the four adjacent walls and located at eachend of the enclosure; a screen located in the front side area, furthercomprising an active area for receiving and converting electromagneticradiation into light; at least one screen located in the interiorportion of the enclosure; and a photodetector, positioned in theinterior of the enclosure, having an active area responsive to thelight.

In one embodiment, the front side area is formed from at least one ofthe plurality of screens. In another embodiment, the active area on eachof the plurality of screens comprises a scintillator material, where thescintillator material is calcium tungstate. In one embodiment, thephotodetector is a photomultiplier tube.

In one embodiment, the detection system enclosure is capable ofreceiving, but not leaking electromagnetic radiation. In anotherembodiment, the interior surface of the adjacent enclosing walls islight reflective.

In one embodiment, the active area of at least one of the plurality ofscreens is larger than the active area of the photodetector and theareal density is 80 mg/cm².

In one embodiment, the surface geometry of at least one of the pluralityof screens is straight or smooth. In another embodiment, the surfacegeometry of at least one of the plurality of screens is irregular. Inyet another embodiment, the surface geometry of at least one of theplurality of screens is contoured. In still another embodiment, thesurface geometry of at least one of the plurality of screens iscorrugated.

In one embodiment the surface geometry of the at least one screen ispyramidal. In another embodiment the surface geometry of the at leastone screen is conical. In a yet another embodiment the surface of the atleast one screen comprises a plurality of fish-scale like scintillatingelements. In a still another embodiment the surface configuration of theat least one screen is in the form of hexagonal beehive like elements.

In another embodiment, the present invention is a radiant energy imagingsystem comprising: a radiation source; a detection system, comprising i)an enclosure having four adjacent walls, connected to each other at anangle and forming a rectangle and interior portion of the enclosure; ii)a front side area and a back side area formed from the four adjacentwalls and located at each end of the enclosure; iii) a plurality ofscreens, wherein each screen further comprises an active area forreceiving and converting electromagnetic radiation into light; and iv) aphotodetector, positioned in the interior of the enclosure, having anactive area responsive to the light; an image processor for receivingsignals from the photodetector and generating an image; and a displayfor displaying the image generated. In one embodiment, the radiantenergy imaging system is a people screening system. In anotherembodiment, the radiant energy imaging system is a baggage screeningsystem.

In a yet another embodiment, the present invention is a dual screendetection system for detecting electromagnetic radiation comprising: anenclosure having three adjacent side walls forming a front side area, asecond side area and a third side area. The three adjacent side wallsare connected to each other at an angle and form an enclosure having atriangular cross-section. The three adjacent side walls are alsoconnected to a top and bottom areas. The front side area faces theobject or subject under inspection and comprises a first screen. Thesecond side area further comprises a second screen located in theinterior of the enclosure. A photomultiplier tube is placed proximate tothe third side area. The back-end electronics and cables associated withthe photomultiplier tube are enclosed in a housing that is formed by thethird side area and a substantially semi-circular side.

In one embodiment the aforementioned detector enclosures are deployed inthe form of modular tear-drop panels, cabinets or towers providing acontemporary and aesthetic look. In one embodiment, the presentinvention is a radiant energy imaging system in the form of asingle-sided walk-by secure stand-off for screening human subjectscomprising: two dual screen detector enclosures embodied in the form ofmodular cabinets, towers or panels. Another modular housing encloses aradiation source. The two dual screen detector towers are placedsymmetrically on both sides of an opening in the radiation sourcehousing. The opening allows a narrow pencil beam of X-rays to impingeupon a subject. The backscattered X-ray photons are captured by the twodetector towers for imaging.

According to an object of the present invention, the walk-by stand-offpeople screening system has modular components that can be disassembledfor mobility and easy transportation and reassembled again at the siteof interest. Thus, the tear drop detector towers and the radiationsource housing with associated electronics and cables are manufacturedas separate modules or cabinets that can be integrated quickly to formthe screening system.

In one embodiment, the present invention is a detection system fordetecting electromagnetic radiation comprising: an enclosure having twoadjacent walls, each having interior surfaces, a first end and a secondend, wherein the first ends of the two adjacent walls are connected atan angle to form an interior and wherein the second ends of the twoadjacent walls are connected to a semi-circular housing; at least onesubstrate, positioned on each of said interior surfaces of the adjacentwalls, wherein each substrate further comprises an active area forreceiving and converting electromagnetic radiation into light; and aphotodetector, positioned in the interior portion of the semi-circularhousing, wherein said photodetector has an active area responsive to thelight. The two adjacent walls enclose a volume having a form of atriangular prism. The interior surfaces of the adjacent walls are lightreflective. The active area on each of the substrates comprises ascintillator material. The scintillator material is calcium tungstate.

The active area of at least one of the substrates is larger than theactive area of the photodetector. The surface geometry of at least oneof the substrates is at least one of smooth, pyramidal, hexagonal,conical, fan-shaped, irregular, contoured, or corrugated. Thephotodetector is a photomultiplier tube.

In another embodiment, the present invention is a detection system fordetecting electromagnetic radiation comprising: a first enclosure havingtwo adjacent walls, each having interior surfaces, a first end and asecond end, wherein the first ends of the two adjacent walls areconnected at an angle to form an interior and wherein the second ends ofthe two adjacent walls are connected to a semi-circular housing; atleast one substrate, positioned on each of said interior surfaces of theadjacent walls, wherein each substrate further comprises an active areafor receiving and converting electromagnetic radiation into light; and aphotodetector, positioned in the interior portion of the semi-circularhousing, wherein said photodetector has an active area responsive to thelight; and a second enclosure having two adjacent walls, each havinginterior surfaces, a first end and a second end, wherein the first endsof the two adjacent walls are connected at an angle to form an interiorand wherein the second ends of the two adjacent walls are connected to asemi-circular housing; at least one substrate, positioned on each ofsaid interior surfaces of the adjacent walls, wherein each substratefurther comprises an active area for receiving and convertingelectromagnetic radiation into light; and a photodetector, positioned inthe interior portion of the semi-circular housing, wherein saidphotodetector has an active area responsive to the light.

The first enclosure and said second enclosure are positioned next toeach other and separated by an elongated member. The elongated membercomprises a slit configured to pass X-ray radiation. The two adjacentwalls in said first enclosure enclose a volume having a form of atriangular prism. The interior surfaces of the adjacent walls in saidsecond enclosure are light reflective. The active area on each of thesubstrates in said first enclosure and said second enclosure comprises ascintillator material. The scintillator material is calcium tungstate.The active area of at least one of the substrates in said firstenclosure and said second enclosure is larger than the active area ofthe photodetector. The surface geometry of at least one of thesubstrates in said first enclosure and said second enclosure is at leastone of smooth, pyramidal, hexagonal, conical, fan-shaped, irregular,contoured, or corrugated. The photodetector in the first enclosure is aphotomultiplier tube.

In another embodiment, the present specification discloses a detectorsystem comprising: an enclosed interior volume defined by a) a firstside having a first end and a second end; b) a second side having afirst end and a second end, wherein the first end of the first side isattached to the first end of the second side and forms an acute anglewith respect thereto; c) a curved section having a first end and asecond end, wherein the first end of the curved section is attached tothe second end of the second side and wherein the second end of thecurved section is attached to the second end of the first side, d) afirst substrate positioned on an interior surface of the first side,wherein the first substrate further comprises an active area forreceiving and converting radiation into light; e) a second substratepositioned on an interior surface of the second side, wherein the secondsubstrate further comprises an active area for receiving and convertingradiation into light; and f) at least one photodetector.

Optionally, the photodetector comprises a light responsive area and anon-light responsive area and wherein the light responsive area ispositioned to receive the light emitted from the first substrate and thesecond substrate. The non-light responsive area is positioned within thecurved section. The attachment of the first end of the curved section tothe second end of the second side or the attachment of the second end ofthe curved section to the second end of the first side is hinged. Thecurved section is adapted to be rotated relative to said hinge. Thephotodetector comprises a light responsive area and a non-lightresponsive area and wherein the light responsive area is positioned toreceive the light emitted from the first substrate and the emitted fromthe second substrate. Upon the curved section being rotated relative tosaid hinge, said non-light responsive area is accessible from outsidethe enclosed interior volume.

In another embodiment, the present specification discloses a detectorsystem comprising: a) a first side defined by a planar surface having anexterior surface facing a subject under inspection and an interiorsurface, wherein the first side is configured to receive radiationbackscattered from said subject; b) a second side in an acute angularrelationship with said first side, wherein said second side is definedby a planar surface having an interior surface adapted to receiveradiation passing through the first side and wherein said second side isconfigured to only receive radiation after it passes through said firstside; c) a first substrate positioned on the interior surface of thefirst side, wherein the first substrate further comprises an active areafor receiving and converting said radiation into light; d) a secondsubstrate positioned on the interior surface of the second side, whereinthe second substrate further comprises an active area for receiving andconverting said radiation into light; and e) at least one photodetectorhaving a light responsive area and a non-light responsive area, whereinthe light responsive area is positioned to receive the light emittedfrom the first substrate and the second substrate.

Optionally, the radiation comprises X-ray photons. The first substratedetects 30-60% of the X-ray photons impinging on said first side. Thesecond substrate detects 10-30% of the X-ray photons impinging on saidfirst side.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will beappreciated, as they become better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings, wherein:

FIG. 1 is a front view illustration of a conventional detectorenclosure, having one screen;

FIGS. 2 a and 2 b illustrate the incidence of electromagnetic radiationon a first screen of a conventional detector enclosure;

FIG. 3 illustrates one embodiment of the detector enclosure of thepresent invention, having a plurality of screens, showing the incidenceof electromagnetic radiation on the plurality of screens;

FIG. 4 illustrates another embodiment of the detector enclosure of thepresent invention, having a plurality of screens, showing the incidenceof electromagnetic radiation on the plurality of screens;

FIG. 5 illustrates one embodiment of a backscatter inspection system inwhich any of the detector enclosures of the present invention can beimplemented;

FIG. 6 illustrates one embodiment of a traditional transmission X-rayscreening system in which any of the detector enclosures of the presentinvention can be implemented;

FIG. 7 illustrates one embodiment of the detector enclosure of thepresent invention, comprising at least two screens;

FIG. 8 shows perspective view of an embodiment of the detector enclosureof FIG. 7;

FIG. 9 a shows front-side perspective view of one embodiment of awalk-by people screening system;

FIG. 9 b shows a top cross-sectional view of the walk-by off peoplescreening system;

FIG. 10 a shows embodiments where the surface geometry of the at leastone screen is pyramidal;

FIG. 10 b shows screen surface configurations for pyramidal surfacegeometry;

FIG. 11 shows an embodiment where the surface geometry of the at leastone screen comprises conical scintillating elements; and

FIG. 12 shows an embodiment where the surface geometry of the at leastone screen comprises fish-scale like scintillating elements; and

FIG. 13 shows an embodiment where the surface configuration of the atleast one screen is in the form of hexagonal or beehive like elements.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed towards several embodiments of anelectromagnetic radiation detector in which a plurality of screens isemployed. The present invention is directed towards a detection systemenclosure having at least one screen. Electromagnetic radiation isabsorbed by the screen which emits light photons that are detected by aphotomultiplier tube located within the enclosure. In one embodiment,the detection system of the present invention has one screen located atthe front of the enclosure and at least one screen located in theinterior of the enclosure. In one embodiment, the at least one screencomprises an active area for receiving and converting electromagneticradiation into light (photons). In one embodiment, the active area ofthe at least one screen comprises a scintillator material. In oneembodiment, the scintillator material is calcium tungstate.

In one embodiment, the at least one screen has a thickness (arealdensity) of 80 mg/cm². In one embodiment, the surface geometry of the atleast one screen is straight or smooth. In one embodiment, the surfacegeometry of the at least one screen is irregular. In another embodiment,the surface geometry of the at least one screen is contoured. In anotherembodiment, the surface geometry of the at least one screen iscorrugated; a corrugated surface geometry provides a greater surfacearea for receiving and converting electromagnetic radiation into light,by allowing for an increase in the electromagnetic radiation path lengthwithout increasing the light output path length, for maximum detectionefficiency. It should be understood by those of ordinary skill in theart that any surface geometry may be used for the screen to increase theamount of electromagnetic radiation absorbed.

The present invention is also directed towards the use of at least onescreen in the interior of the enclosure, thus increasing the amount ofelectromagnetic radiation reaching the detector, and subsequently, theamount of photons reaching the photomultiplier. In one embodiment, theat least one screen located in the interior of the enclosure hassubstantially identical specifications to the screen located in thefront of the enclosure. In one embodiment, the at least one screenpositioned in the interior of the enclosure is different from the screenlocated in the front of the enclosure, in terms of at least one ofchemical composition, surface geometry, thickness and energy response.The use of a screen at the front of the enclosure and the at least onescreen in the interior of the enclosure increases the amount ofelectromagnetic radiation absorbed and therefore, the number of photonsgenerated, further improving detection capability, and thus imagequality.

Thus, the present invention is directed towards a detector configurationthat maximizes the efficiency of the detector material. Detectionefficiency is a measure of the efficiency of the detector screen, or,the probability that electromagnetic radiation will be absorbed by thescreen to produce light photons detectable by the photomultiplier tube.X-ray detectors need to interact with incident X-ray photons to recordtheir presence; X-rays that pass through the detector withoutinteraction are wasted. Detection efficiency is mainly determined by theinteraction probability of the photons with the detector material andthe thickness of the material. The following equation can be used tocalculate the efficiency of a detector:

I=I ₀ *e ^(−μx)

where I₀ is the number of photons of a certain energy incident orentering the slab of material; x is the thickness of the slab, I is thenumber of photons that have passed through a layer of thickness x, and μis the linear attenuation coefficient of the material for photons ofthis particular energy.

The photons that do not get through have interacted within the slab ofmaterial and are either absorbed or scattered. The number of photonsabsorbed by a certain thickness is the difference I0-I. However, insteadof calculating for different I's, the ratio of (I0-I)/I is calculatedand it is called the “Percent Absorption.” Conventional screenstypically achieve far less than 100% efficiency. The present inventionis directed toward absorbing more of the otherwise wasted X-ray photonsand thereby improving the detection capability.

In another embodiment, the present invention is also directed towards adetection system enclosure that further comprises a photo-multipliertube, positioned in the interior of the enclosure, having an active arearesponsive to the light. In another embodiment, the active area of theat least one screen is larger than the active area of thephoto-multiplier tube so that the amount of electromagnetic radiationabsorbed is maximized.

The present invention is directed towards multiple embodiments. Languageused in this specification should not be interpreted as a generaldisavowal of any one specific embodiment or used to limit the claimsbeyond the meaning of the terms used therein. Reference will now be madein detail to specific embodiments of the invention. While the inventionwill be described in conjunction with specific embodiments, it is notintended to limit the invention to one embodiment.

FIG. 1 is a front view illustration of a conventional detectorenclosure, having one screen. In one embodiment, detector 100 comprisesan enclosure having four adjacent walls, 102 a, 102 b, 102 c, and 102 d,connected to each other at an angle. In one embodiment, the fouradjacent walls 102 a, 102 b, 102 c, and 102 d form a rectangular shape.In one embodiment, the rectangular shape is a trapezium-like shape.Adjacent walls 102 a, 102 b, 102 c, and 102 d further form a front sidearea 106 and a back side area 104 at the ends of the enclosure.

In one embodiment, the enclosure formed from adjacent walls 102 a, 102b, 102 c, 102 d, front side area 106 and back side area 104 is capableof receiving, but not leaking electromagnetic radiation, therebyblocking the exit of incoming radiation from a radiation source. In oneembodiment, the ability of the enclosure to receive, and not leak,radiation, is facilitated by the light reflective interiors of theenclosing walls. In one embodiment, the interiors of walls 102 a, 102 b,102 c, and 102 d are painted white so that they are highly lightreflective.

In one embodiment, front side area 106 of detector enclosure 100 is usedfor receiving radiation and thus faces the object under inspection whenin use in an exemplary scanning system, as described in detail withrespect to FIGS. 5 and 6 below. In one embodiment, front side area 106further comprises screen 107.

In addition, detector enclosure 100 further comprises photo-detector108, placed in the interior of the enclosure proximate to back side area104. In one embodiment, the photo-detector 108 is a photomultipliertube. Photomultiplier tubes are well-known to those of ordinary skill inthe art and will not be discussed herein.

FIGS. 2 a and 2 b illustrate the incidence of electromagnetic radiationon a first screen of a conventional detector enclosure. In operation,the screening system directs electromagnetic radiation from a sourcetoward a subject or object under inspection such that the X-rays areincident upon the subject or object. The X-rays are then, depending uponthe intensity of the X-ray and the type of inspection system beingemployed, scattered from or transmitted through the subject or objectunder inspection. The radiation source and the nature of the X-ray beamare described in detail with respect to FIGS. 5 and 6 below and will notbe discussed herein.

Now referring to FIG. 2 a scattered or transmitted X-rays 210 reach thedetector enclosure 200 and first impinge upon screen 207. Screen 207absorbs at least a portion of the scattered or transmitted X-rays 210and converts the X-rays into light photons 206 in the interior ofdetector enclosure 200.

As shown in FIG. 2 b, however, some of the X-rays are not absorbed andthus pass through screen 207. In addition, in a conventional detectorenclosure with only one front screen, at least a portion of photons 206reflect off of the highly reflective interior walls of the enclosure andare subsequently detected by photomultiplier tube 208.

In one embodiment, as described in greater detail with respect to FIG. 3below, the present invention is a detector enclosure comprising at leastone additional screen (not shown in FIGS. 2 a and 2 b) in the interiorof the enclosure. The at least one additional screen further increasesthe exposure rate of the scattered or transmitted X-rays 210. The neteffect of the at least one additional screen is to increase thephoto-detection efficiency of photomultiplier tube 208 by absorbing moreelectromagnetic radiation, subsequently converting that radiation tolight, and thus, providing the photomultiplier tube with a strongersignal to detect.

FIG. 3 illustrates one embodiment of the detector of the presentinvention, having a plurality of screens. Detector enclosure 300 issimilar to the enclosure described with respect to FIG. 1, in that itcomprises four adjacent side walls (not fully shown in FIG. 3) whichform a front side area 306 and a back side area 304. The enclosure willnot be described in further detail herein. One of ordinary skill in theart should appreciate that the present invention can be used with thedetector enclosure of FIG. 1 or modified so as not to depart from theinvention described herein.

Referring now to FIG. 3, first screen 307 a is located on the front sidearea 306 of detector enclosure 300. In one embodiment, second and thirdscreens 307 b and 307 c are positioned inside the detector enclosure300. The X-rays scattered from or transmitted through the subject orobject under inspection 310 first impinge upon first screen 307 a ofdetector enclosure 300. Some of the scattered or transmitted X-rays,however, are not absorbed by first screen 307 a and thus pass throughfirst screen 307 a.

To increase detection efficiency, in one embodiment, detector enclosure300 further comprises second and third screens, 307 b and 307 c,respectively in the interior of the enclosure. Second and third screens,307 b and 307 c, respectively, further increase the exposure rate andthus, absorption of the scattered or transmitted X-rays 310. The overalleffect of the first, second, and third screens is an increase in thephoto-detection efficiency of photomultiplier tube 308 by absorbing moreelectromagnetic radiation, subsequently converting that radiation tolight, and thus, providing the photomultiplier tube with a strongersignal to detect.

In one embodiment, first screen 307 a comprises an active area forreceiving and converting electromagnetic radiation into light (photons).In one embodiment, first screen 307 a is a fluorescent chemical screen.In one embodiment, scintillators in the fluorescent chemical screen 307a detect a large fraction of the incident radiation, produce significantlight output to the photomultiplier tube, and exhibit a temporal decaytime which is short compared to the pixel to pixel scanning rate of theradiation beam.

In one embodiment, the fluorescent chemical screen includes calciumtungstate. Generally, a calcium tungstate screen has a relatively shortdecay time of 10 microseconds that allows rapid scanning of theradiation beam with minimal image degradation. The calcium tungstatescreen is capable of detecting approximately 70% of the backscattered ortransmitted radiation, and thus, produces approximately 250 usable lightphotons per 30 KeV X-ray.

Additionally, the use of a thicker screen enables the detection of moreof the radiation incident upon the detector at the expense of lowerlight output. In one embodiment, the areal density of the screen is 80milligrams per square centimeter.

In one embodiment, the at least one screen located in the interior ofthe enclosure has identical specifications to the screen located in thefront of the enclosure. Thus, in one embodiment, second and thirdscreens 307 b and 307 c, respectively, are identical to first screen 307a. In one embodiment, the at least one screen positioned in the interiorof the enclosure is different from the screen located in the front ofthe enclosure, in terms of at least one of chemical composition, surfacegeometry, thickness and energy response. Thus, in one embodiment, secondand third screens 307 b and 307 c, respectively, are different fromfirst screen 307 a.

Although exemplary screens have been described above, it should be notedthat the characteristics of the screen can vary widely in terms ofchemical composition, surface geometry, thickness and energy response,and that any type of screen may be used in the present invention, aswould be evident to those of ordinary skill in the art.

FIG. 4 illustrates another embodiment of the detector enclosure of thepresent invention, having a plurality of screens. In one embodiment, thesurface geometry of the at least one screen is straight or smooth. Inone embodiment, the surface geometry of the at least one screen isirregular. In another embodiment, the surface geometry of the at leastone screen is contoured. In another embodiment, the surface geometry ofthe at least one screen is corrugated. A corrugated surface geometryprovides a greater surface area for receiving and convertingelectromagnetic radiation into light, by allowing for an increase in theelectromagnetic radiation path length without increasing the lightoutput path length, for maximum detection efficiency. FIG. 10 a showsembodiments where the surface geometry of the at least one screen ispyramidal 1000. FIG. 10 b shows exemplary screen surface configurations1005 and 1010 for pyramidal surface geometry. FIG. 11 shows anotherembodiment, where the surface geometry of the at least one screencomprises conical scintillating elements 1100. FIG. 12 shows yet anotherembodiment, where the surface geometry of the at least one screencomprises fan-shaped or fish-scale like scintillating elements 1200.FIG. 13 shows a still another embodiment where the surface configurationof the at least one screen is in the form of hexagonal or beehive likeelements 1300 that is formed by deposition process of scintillationmaterial on screen mould 1305. It should be understood by those ofordinary skill in the art that any surface type may be used for thescreen to increase the amount of electromagnetic radiation absorbed.

In one embodiment, screen 407 located on front side area 404 of detectorenclosure 400 is corrugated. The corrugated surface of screen 404provides a greater surface area for absorbing scattered or transmittedelectromagnetic radiation 410, incident upon the detector enclosure 400.It should be noted that because light generated in spaces 411, definedby screens 407 and 408, cannot escape easily, the detection efficiency,or effective detection area is reduced.

FIG. 5 illustrates one embodiment of a scanning system in which any ofthe detector enclosures of the present invention can be implemented. Inone embodiment, the detector enclosure of the present invention isemployed in a backscatter X-ray scanning system, such as but not limitedto a people screening system. In one embodiment, inspection system 500comprises radiation source 508 and at least one detector enclosure 502.As described in detail above, the at least one detector enclosure 502may comprise any number of arrangements including, but, not limited toat least one detector screen. In addition, at least one detectorenclosure 502, in another embodiment, may comprise any number ofarrangements including, but, not limited to a plurality of detectorscreens. While various arrangements of detectors will not be repeatedherein, it should be understood by those of ordinary skill in the artthat any number of detector arrangements can be employed, as describedabove and the exemplary embodiment is not intended to limit the presentinvention.

Referring back to FIG. 5, X-ray source 508 is used to generateradiation. In one embodiment, X-ray source 508 is employed to generate anarrow pencil beam 506 of X-rays directed towards an object or subjectunder examination 504. In one embodiment, pencil beam is formed with theintegration of an x-ray tube, a mechanical chopper wheel, and a slit.

In one embodiment, X-ray source 508 operates with an empirically andtheoretically determined optimum X-ray tube potential of 50 KeV and 5milliamps, resulting in X-rays of approximately 30 KeV. The vertical andhorizontal dimension of the X-ray beam is approximately six millimeters(6 mm) where it strikes subject 504. Subject 504 is a body that is beingsubjected to X-ray imaging. In one embodiment, subject 504 is a human.In another embodiment, subject 504 is an object. Initially, X-ray beam506 strikes only the body of subject 504. Many of the X-rays penetrate afew centimeters into the body, interact by Compton scattering, and exitthe body through the same surface that they entered. X-ray sensitivedetector enclosures 502 are placed symmetrically around incident X-raypencil beam to detect backscattered X-rays 510 and provide an electronicsignal characteristic of the X-ray reflectance. It should be understoodto those of ordinary skill in the art that any number of ionizingradiation sources may be used, including but not limited to gammaradiation, electromagnetic radiation, and ultraviolet radiation.

Detectors 502 are positioned for uniform X-ray detection on all sides ofX-ray beam 506. In one embodiment, arrays of detectors 502 are placedaround source 508 for uniform detection of backscattered rays 510.Detectors 502 include an enclosure capable of enclosing or “trapping”scattered rays 510. A photo-detector generates electronic signals inresponse to detected rays that are initially converted into light.Details about the structure and operation of several embodiments of adetector 502 are discussed in detail with respect to FIGS. 1-4 and willnot be repeated herein.

In one embodiment, each detector 502 produces electronic signals whichare directed to a processor. The processor analyzes the received signalsand generates an image on a display means 512. The intensity at eachpoint in the displayed image corresponds to the relative intensity ofthe detected scattered X-rays. In one embodiment, X-ray source 508communicates synchronization signals to the processor. The processoranalyzes the detected signals and compares them to the synchronizationsignals to determine the display image.

In one embodiment, display means 512 is a monitor and is employed todisplay graphical images signaled by the processor. Display means 512can be any display or monitor as commonly known in the art, including acathode ray tube monitor or an LCD monitor. In one embodiment, thedigitized scatter image displayed by display means 512 preferablyconsists of 480 rows by 160 columns with 8 bits per pixel.

Referring back to FIG. 5, detectors 502 are separated by an openingthrough which X-ray beam 506 passes before striking subject 504. In oneembodiment, detectors 502 can move in a vertical direction while X-raybeam 506 moves in a horizontal direction by movement of X-ray source 508in the horizontal direction. However, the placement and movement ofdetectors 502 and source 508 is not limited to the description providedherein. In other embodiments, detectors 502 and source 508 can be placedand moved by any method as is commonly known in the art. Theintersection of X-ray beam 506 and subject 504 defines an image pictureelement (pixel) of a specified area.

FIG. 6 illustrates another embodiment of a scanning system in which anyof the detector enclosures of the present invention can be implemented.In another embodiment, the scanning system is a traditional X-rayscanning system, in which X-rays are transmitted through the objectunder inspection. In one embodiment, the traditional transmission X-rayscanning system is a baggage scanning system.

In one embodiment, inspection system 600 comprises radiation source 608and at least one detector enclosure 602. As described in detail above,the at least one detector enclosure 602 may comprise any number ofarrangements including, but, not limited to at least one detectorscreen. In addition, at least one detector enclosure 602, in anotherembodiment, may comprise any number of arrangements including, but, notlimited to a plurality of detector screens. While various arrangementsof detectors will not be repeated herein, it should be understood bythose of ordinary skill in the art that any number of detectorarrangements can be employed, as described above and the exemplaryembodiment is not intended to limit the present invention.

Referring back to FIG. 6, X-ray source 608 is used to generateradiation. In one embodiment, X-ray source 608 is employed to generate anarrow pencil beam 606 of X-rays directed towards an object or subjectunder examination 604. In one embodiment, pencil beam is formed with theintegration of an x-ray tube, a mechanical chopper wheel, and a slit.

Object 604 is an item that is subjected to X-ray imaging. In oneembodiment, object 604 is a piece of luggage or carry-on baggage.Initially, X-ray beam 606 strikes only the object 604. Many of theX-rays are transmitted through the object, interact by Comptonscattering, and exit the object through the opposite surface that theyentered. X-ray sensitive detector enclosures 602 are placedsymmetrically around incident X-ray pencil beam to detect transmittedX-rays 610 and provide an electronic signal characteristic of the X-raytransmission.

It should be understood to those of ordinary skill in the art that anynumber of ionizing radiation sources may be used, including but notlimited to gamma radiation, electromagnetic radiation, and ultravioletradiation.

Detectors 602 are positioned for uniform X-ray detection on all sides ofX-ray beam 606. In one embodiment, arrays of detectors 602 are placedaround object 604 for uniform detection of transmitted rays 610.Detectors 602 include an enclosure capable of enclosing or “trapping”scattered rays 610. A photo-detector generates electronic signals inresponse to detected rays that are initially converted into light.Details about the structure and operation of several embodiments of adetector 602 are discussed in detail with respect to FIGS. 1-4 and willnot be repeated herein.

In one embodiment, each detector 602 produces electronic signals whichare directed to a processor. The processor analyzes the received signalsand generates an image on a display means 612. The intensity at eachpoint in the displayed image corresponds to the relative intensity ofthe detected transmitted X-rays. In one embodiment, X-ray source 608communicates synchronization signals to the processor. The processoranalyzes the detected signals and compares them to the synchronizationsignals to determine the display image. In one embodiment, display means612 is a monitor and is employed to display graphical images signaled bythe processor. Display means 612 can be any display or monitor ascommonly known in the art, including a cathode ray tube monitor or anLCD monitor. In one embodiment, the digitized image displayed by displaymeans 612 preferably consists of 480 rows by 160 columns with 8 bits perpixel.

In one embodiment, detectors 602 can move in a vertical direction whileX-ray beam 606 moves in a horizontal direction by movement of X-raysource 608 in the horizontal direction. However, the placement andmovement of detectors 602 and source 608 is not limited to thedescription provided herein. In other embodiments, detectors 602 andsource 608 can be placed and moved by any method as is commonly known inthe art. The intersection of x-ray beam 606 and object 604 defines animage picture element (pixel) of a specified area.

FIG. 7 illustrates one embodiment of the detector enclosure 700 of thepresent invention, comprising at least two screens. The dual screendetector enclosure 700 comprises three adjacent side walls which form afront side area 701, second side area 702 and third side area 703. Walls701, 702 and 703 are connected to each other at an angle, thereby,forming an enclosure of triangular cross-section. Adjacent walls 701,702 and 703 further form a top area 704 and a bottom area 705.

In one embodiment, the enclosure formed from adjacent walls 701, 702,703, top area 704 and bottom area 705 is capable of receiving, butsubstantially not leaking electromagnetic radiation, thereby blockingthe exit of incoming radiation from a radiation source.

In one embodiment, front side area 701 of detector enclosure 700 is usedfor receiving radiation 715 and thus faces the object or subject underinspection when in use in an exemplary scanning system, as described indetail with respect to FIGS. 9 a and 9 b. In one embodiment, front sidearea 701 further comprises screen 707. Second side area 702 comprises anadditional screen 708 in the interior of the enclosure 700. Detectorenclosure 700 further comprises a photo-detector 709, placed in theinterior of the enclosure, which in one embodiment, is proximate tothird side area 703. In one embodiment, the photo-detector 709 is aphotomultiplier tube having a light responsive area and a non-lightresponsive area. Photomultiplier tubes are well-known to those ofordinary skill in the art and will not be further discussed herein.

In one embodiment, backside portion of the photomultiplier tubecomprising associated electronics is enclosed in housing 710. In oneembodiment, housing 710 is formed by the third side area 703 and a side711 which has a substantially semi-circular cross-section when viewedfrom the top. The top and bottom sides of the substantiallysemi-circular housing 710 are also covered by walls. In one embodiment,the substantially semi-circular side 711 is connected, at one end, tothe side area 703 by hinged joints 712 such that the side 711 can beopened with respect to the hinged end allowing for easy access to thephotomultiplier electronics for inspection, repair and maintenance.

The X-rays 715 scattered from or transmitted through the subject orobject under inspection first impinge upon first screen 707 of detectorenclosure 700. Some of the scattered or transmitted X-rays, however, arenot absorbed by first screen 707 and thus pass through first screen 707.To increase detection efficiency, detector enclosure 700 furthercomprises a second screen 708 in the interior of the enclosure. Secondscreen 708 further increase the exposure rate and thus, absorption ofthe scattered or transmitted X-rays 715. The overall effect of the firstand second screens is an increase in the photo-detection efficiency ofphotomultiplier tube 709 by absorbing more electromagnetic radiation,subsequently converting that radiation to light, and thus, providing thephotomultiplier tube with a stronger signal to detect.

FIG. 8 shows perspective view of an embodiment of the detector enclosure700 of FIG. 7. As shown in FIG. 8, in one embodiment, the detectorenclosure is formed as a modular dual screen detector tower, cabinet orpanel 800. In the current view, the front side area 801 and thesubstantially semi-circular side 811 are visible. The semi-circular side811 is connected to side 801 by hinges 812. The detector towers 800,deployed in the form of cabinets or panels have an additional advantageof providing a pleasant aesthetic appearance.

FIG. 9 a shows front-side perspective view of one embodiment of ascanning system 900 in which the detector enclosure 700 of FIG. 7 can beimplemented. In one embodiment, the detector enclosure of the presentinvention is employed in a backscatter X-ray scanning system, such asbut not limited to a people screening system. In one embodiment, thepeople screening system is embodied as a single-sided walk-by securestand-off 900.

Persons of ordinary skill in the art should appreciate that while thewalk-by secure stand-off people screening system 900 is described toillustrate the implementation of detector enclosure 700 of FIG. 7, anyof the detector enclosures of the present invention can be used with thesystem 900 without any limitations.

FIG. 9 b shows a top cross-sectional view of one embodiment of thedetector screens of the system of the present invention as used in awalk-by people screening system 900. Reference will now be made to FIGS.9 a and 9 b simultaneously to describe various elements of the system900.

In one embodiment, inspection system 900 comprises first and seconddetector enclosures 905 and 910 respectively. In one embodiment, thedetector enclosures are embodied in the form of modular dual screendetector towers 800 of FIG. 8. In alternate embodiments, the detectorenclosures may comprise any number of arrangements including, but, notlimited to a plurality of detector screens. As visible in FIG. 9 b, thedetector towers 905 and 910 comprise front side area 901, second sidearea 902 and third side area 903 that are connected to each other at anangle to form a triangular cross-section. The front side area 901comprises screen 907 (or any light responsive substrate) and facessubject 920 under inspection. The second side area 902 comprises asecond screen 908 (or any light responsive substrate) in the interior ofthe towers. Each of the towers 905, 910 comprises photomultiplier tubes909 that are placed in the interior of the towers proximate to thirdside area 903. The back-end electronics of the photomultiplier tubes 909(portion not responsive to light) is housed in the substantiallysemi-circular housing 911, which is connected to the two angled sides901, 902 of the detector towers, by hinges.

A radiation source 948 is enclosed in another modular housing 915(visible in FIG. 9 b). X-ray source 948 is used to generate radiation.In one embodiment, X-ray source 948 is employed to generate a narrowpencil beam 930 of X-rays directed towards the subject 920 underexamination. In one embodiment, subject 920 is a human. In oneembodiment, pencil beam is formed with the integration of an X-ray tube,a mechanical chopper wheel, and a slit. It should be understood to thoseof ordinary skill in the art that any number of ionizing radiationsources may be used, including but not limited to gamma radiation,electromagnetic radiation, and ultraviolet radiation.

Referring to cross-sectional top view of the housing 915 in FIG. 9 b,the housing 915 comprises first and second angled sides 916, 917 suchthat they abut and coincide with the sides 902 of the detector towers905 and 910, when the detector towers and the radiation source housingare integrated or assembled together. A front-end side strip 918 facingthe subject 920 comprises an opening 925 (visible in FIG. 9 a) throughwhich X-ray beam 930 passes before striking subject 920. Limited opening925 aids in the reduction of electromagnetic interference and radiationnoise. The side strip 918 also acts as a separator for the two detectortowers such that the two detector towers are assembled symmetricallyaround incident X-ray pencil beam 930 to detect backscattered X-rays 935and provide an electronic signal characteristic of the X-rayreflectance.

In one embodiment, the inspection system 900 has modular components thatcan be disassembled for mobility and easy transportation and thenreassembled again at the site of interest. Thus, the tear drop detectortowers 905, 910 and the radiation source housing 915 with associatedelectronics and cables are manufactured as separate modules or cabinetsthat can be integrated quickly to form the system 900.

During operation, as the subject 920 physically passes the detectortowers 905, 910 a portion of the pencil beam 930 of X-rays that strikesthe subject 920 are back-scattered, as rays 935, due to Comptonscattering and impinge on the first screen 907 at the front side area901 of the detector towers. While a portion of the scattered X-rays aredetected by the first screen 907, some portion of theses get transmittedthrough the first screen 907 without being detected and impinge on thesecond screen 908 (at side 902) in the interior of the detector towers.In one embodiment approximately 30-60%, and more preferablyapproximately 40%, of the X-ray photons impinging the first screen 907are detected by it while approximately 10-30%, and more preferablyapproximately 24%, of the X-ray photons are detected by the secondscreen 908. The photomultiplier tubes 909 generate electronic signals inresponse to detected rays that are initially converted into light. Thelight emitted by scintillation at screens 907, 908 is bounced around thetriangular enclosures/towers 905, 910 until captured with thephotomultipliers 909. Details about the structure and operation ofdetector towers 905, 910 are discussed in detail with respect to FIGS. 7and 8 and will not be repeated herein.

The electronic signals produced by the two detector towers 905, 901 aredirected to a processor. The processor analyzes the received signals andgenerates an image on a display means (not shown). The intensity at eachpoint in the displayed image corresponds to the relative intensity ofthe detected scattered X-rays. In one embodiment, X-ray source 908communicates synchronization signals to the processor. The processoranalyzes the detected signals and compares them to the synchronizationsignals to determine the display image. In one embodiment, display meansis a monitor and is employed to display graphical images signaled by theprocessor. Display means can be any display or monitor as commonly knownin the art, including a cathode ray tube monitor or an LCD monitor. Inone embodiment, the digitized scatter image displayed by display meanspreferably consists of 480 rows by 160 columns with 8 bits per pixel.

The above examples are merely illustrative of the many applications ofthe system of present invention. Although only a few embodiments of thepresent invention have been described herein, it should be understoodthat the present invention might be embodied in many other specificforms without departing from the spirit or scope of the invention.Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope of theappended claims.

1. A detection system for detecting electromagnetic radiationcomprising: an enclosure having two adjacent walls, each having interiorsurfaces, a first end and a second end, wherein the first ends of thetwo adjacent walls are connected at an angle to form an interior andwherein the second ends of the two adjacent walls are connected to asemi-circular housing; at least one substrate, positioned on each ofsaid interior surfaces of the adjacent walls, wherein each substratefurther comprises an active area for receiving and convertingelectromagnetic radiation into light; and a photodetector, positioned inthe interior portion of the semi-circular housing, wherein saidphotodetector has an active area responsive to the light.
 2. Thedetection system of claim 1 wherein the two adjacent walls enclose avolume having a form of a triangular prism.
 3. The detection system ofclaim 1 wherein the interior surfaces of the adjacent walls are lightreflective.
 4. The detection system of claim 1 wherein the active areaon each of the substrates comprises a scintillator material.
 5. Thedetection system of claim 4 wherein the scintillator material is calciumtungstate.
 6. The detection system of claim 1 wherein the active area ofat least one of the substrates is larger than the active area of thephotodetector.
 7. The detection system of claim 1 wherein the surfacegeometry of at least one of the substrates is at least one of smooth,pyramidal, hexagonal, conical, fan-shaped, irregular, contoured, orcorrugated.
 8. The detection system of claim 1 wherein the photodetectoris a photomultiplier tube.
 9. A detection system for detectingelectromagnetic radiation comprising: a first enclosure having twoadjacent walls, each having interior surfaces, a first end and a secondend, wherein the first ends of the two adjacent walls are connected atan angle to form an interior and wherein the second ends of the twoadjacent walls are connected to a semi-circular housing; at least onesubstrate, positioned on each of said interior surfaces of the adjacentwalls, wherein each substrate further comprises an active area forreceiving and converting electromagnetic radiation into light; and aphotodetector, positioned in the interior portion of the semi-circularhousing, wherein said photodetector has an active area responsive to thelight; and a second enclosure having two adjacent walls, each havinginterior surfaces, a first end and a second end, wherein the first endsof the two adjacent walls are connected at an angle to form an interiorand wherein the second ends of the two adjacent walls are connected to asemi-circular housing; at least one substrate, positioned on each ofsaid interior surfaces of the adjacent walls, wherein each substratefurther comprises an active area for receiving and convertingelectromagnetic radiation into light; and a photodetector, positioned inthe interior portion of the semi-circular housing, wherein saidphotodetector has an active area responsive to the light.
 10. Thedetection system of claim 9 wherein said first enclosure and said secondenclosure are positioned next to each other and separated by anelongated member.
 11. The detection system of claim 10 wherein theelongated member comprises a slit configured to pass X-ray radiation.12. The detection system of claim 9 wherein the two adjacent walls insaid first enclosure enclose a volume having a form of a triangularprism.
 13. The detection system of claim 9 wherein the interior surfacesof the adjacent walls in said second enclosure are light reflective. 14.The detection system of claim 9 wherein the active area on each of thesubstrates in said first enclosure and said second enclosure comprises ascintillator material.
 15. The detection system of claim 14 wherein thescintillator material is calcium tungstate.
 16. The detection system ofclaim 9 wherein the active area of at least one of the substrates insaid first enclosure and said second enclosure is larger than the activearea of the photodetector.
 17. The detection system of claim 9 whereinthe surface geometry of at least one of the substrates in said firstenclosure and said second enclosure is at least one of smooth,pyramidal, hexagonal, conical, fan-shaped, irregular, contoured, orcorrugated.
 18. The detection system of claim 9 wherein thephotodetector in the first enclosure is a photomultiplier tube.
 19. Adetector system comprising: an enclosed interior volume defined by afirst side having a first end and a second end; a second side having afirst end and a second end, wherein the first end of the first side isattached to the first end of the second side and forms an acute anglewith respect thereto; a curved section having a first end and a secondend, wherein the first end of the curved section is attached to thesecond end of the second side and wherein the second end of the curvedsection is attached to the second end of the first side, a firstsubstrate positioned on an interior surface of the first side, whereinthe first substrate further comprises an active area for receiving andconverting radiation into light; a second substrate positioned on aninterior surface of the second side, wherein the second substratefurther comprises an active area for receiving and converting radiationinto light; and at least one photodetector.
 20. The detector system ofclaim 19 wherein the photodetector comprises a light responsive area anda non-light responsive area and wherein the light responsive area ispositioned to receive the light emitted from the first substrate and thesecond substrate.
 21. The detector system of claim 20 wherein thenon-light responsive area is positioned within the curved section. 22.The detector system of claim 19 wherein the attachment of the first endof the curved section to the second end of the second side or theattachment of the second end of the curved section to the second end ofthe first side is hinged.
 23. The detector system of claim 22 whereinthe curved section is adapted to be rotated relative to said hinge. 24.The detector system of claim 23 wherein the photodetector comprises alight responsive area and a non-light responsive area and wherein thelight responsive area is positioned to receive the light emitted fromthe first substrate and the emitted from the second substrate.
 25. Thedetector system of claim 24 wherein, upon the curved section beingrotated relative to said hinge, said non-light responsive area isaccessible from outside the enclosed interior volume.
 26. A detectorsystem comprising: a first side defined by a planar surface having anexterior surface facing a subject under inspection and an interiorsurface, wherein the first side is configured to receive radiationbackscattered from said subject; a second side in an acute angularrelationship with said first side, wherein said second side is definedby a planar surface having an interior surface adapted to receiveradiation passing through the first side and wherein said second side isconfigured to only receive radiation after it passes through said firstside; a first substrate positioned on the interior surface of the firstside, wherein the first substrate further comprises an active area forreceiving and converting said radiation into light; a second substratepositioned on the interior surface of the second side, wherein thesecond substrate further comprises an active area for receiving andconverting said radiation into light; and at least one photodetectorhaving a light responsive area and a non-light responsive area, whereinthe light responsive area is positioned to receive the light emittedfrom the first substrate and the second substrate.
 27. The detectorsystem of claim 26 wherein said radiation comprises X-ray photons. 28.The detector system of claim 27 wherein said first substrate detects30-60% of the X-ray photons impinging on said first side.
 29. Thedetector system of claim 28 wherein said second substrate detects 10-30%of the X-ray photons impinging on said first side.